1. Field of the Invention
This invention relates generally to corpuscular beam microscopes, specifically an electron microscope, and in particular to a scanning transmission electron microscope in which the intensities of hologram zones having positive or negative interference generated by the imaging ray cone of the microscope are separately measured by a detector and the measured values of the intensities are utilized to control a picture display tube monitor.
2. Description of the Prior Art
Scanning transmission electron microscopes ("STEM") are generally known in the art. See, for example, the technical publication of H. Rose, "Phase Contrast in Scanning Transmission Electron Microscopy," 39 Optik pp. 416-436 (1974). As described in the foregoing publication, a hologram is generated in a scanning transmission electron microscope in a plane which is disposed behind the specimen of the irradiated specimen element at any point in time. This hologram is produced as a result of interference which occurs between the imaging ray cone originating at the specimen element and the primary imaging ray cone.
It has been proposed in Rose's article to provide a detector arrangement in the imaging ray cone of such a microscope comprising a partial area detector consisting of several ring zones, and a full area detector disposed in the shadow of the partial area detector. By utilizing an appropriate design, one of these partial detectors will register the positive, i.e., constructive, interference zone of the hologram, and the other partial detector will register the negative, i.e., destructive, interference zone of the hologram. The output signals generated by the two partial detectors can be combined as required.
The present invention is directed to solving the problem of facilitating the foregoing detection operation in a scanning transmission electron microscope and of expanding the field of its possible applications, particularly with respect to resolution and pattern recognition in such microscopes.